Multi-shell emulsion particle

Abstract

A multi-shell emulsion particle of dry state structure having one or more of penetrating pore(s) connecting the surface layer of the particle with the interior of the particle and having a particle diameter of from 0.1 to 5.0 mu preferably from 0.1 to 1.2 mu . The particles can be prepared by emulsion polymerization of a vinyl monomer (a) containing from 5 to 80% by weight of an unsaturated carboxylic acid to obtain a polymer (A), forming a polymer (B) in the presence of a particle consisting of the resultant polymer (A) while adding a vinyl monomer (b) in an amount of 10 times by weight or less and at a rate of 3 times by weight per hour or more for the weight of the polymer (A), and treating the resultant multi-shell emulsion polymer with an alkaline material to neutralize and swell the polymer (A); or, after the neutralization treatment, further forming a polymer (C) by adding and emulsion-polymerizing a vinyl monomer (c) in an amount of 20 times by weight or less for the total weight of the polymer (A) and polymer (B). The emulsion particle is useful as a component of resin compositions for paints, paper-coating and heat-sensitive recording materials.

What is claimed is: 
     
       1. A multi-shell emulsion particle comprising a dry state structure having one or more penetrating pore(s) connecting the surface layer of the particle with the interior of the particle and having a particle diameter of from 0.1 to 5.0μ, prepared by emulsion polymerization of a vinyl monomer (a) comprising from 5 to less than 80% by weight of an unsaturated carboxylic acid to obtain a polymer (A) in particle form, forming a polymer (B) in the presence of a particle consisting Of the resultant polymer (A) while adding a vinyl monomer (b) in an amount of 10 times by weight or less and at a rate of 3 times by weight per hour or more of the weight of the polymer (A), wherein the proportion of carboxylic acid in vinyl monomer (b) is lower than the proportion of carboxylic acid in vinyl monomer (a), and treating the resultant multi-shell emulsion polymer with an alkaline material to neutralize and swell the polymer (A); or, after the neutralization treatment, further forming a polymer (C) by adding and emulsion-polymerizing a vinyl monomer (c) in an amount of 20 times by weight or less of the total weight of the polymer (A) and polymer (B), and containing an unsaturated carboxylic acid in an amount of 3% by weight or less. 
     
     
       2. The emulsion particle of claim 1 wherein the particle has a void in the interior of the particle in a dry state and one or more penetrating pore(s) from the particle surface to the interior void. 
     
     
       3. The emulsion particle of claim 1 wherein the diameter of the particle is in the range of from 0.1 to 1.2μ. 
     
     
       4. The emulsion particle of claim 1 wherein the particle diameter of the polymer (A) is in the range of from 0.08 to 0.2μ. 
     
     
       5. The emulsion particle of claim 1 wherein the amount of the vinyl monomer (b) is from 1 to 10 times by weight for the weight of the polymer (A). 
     
     
       6. The emulsion particle of claim 1 wherein the rate of addition of the vinyl monomer (b) is from 3.5 to 15 times by weight per hour for the weight of the polymer (A). 
     
     
       7. The emulsion particle of claim 1 wherein the amount of the vinyl monomer (c) is in the range of from 1 to 20 times by weight for the total weight of the polymer (A) and the polymer (B).